Many systems comprise a central control and a plurality of remotely controlled modules which bidirectionally communicate control or data information among the members of the group. Such systems may use through the air transmissions of electromagnetic radiation which is not visible to an operator interfacing with the central control. The operator in such situations is usually unable to distinguish which channels are communicating correctly and, thus, must rely on the central control to determine if the channels are operating correctly. These systems may print out error messages relative to communications channel failures, but this type of annunciation of communication errors is not entirely advantageous when the same display is being used for other information transfers to the operator. The operator wants to be assured of the complete integrity of the communication process without the necessity of having to change operating modes to display communication error messages or having such error messages interrupt the display of other information.
Such assurance would be particularly advantageous in a system where the operator is able to select which channels, from among a plurality of channels, communicate with the central control. For example, when information from several channels is combined to form a display of information and those channels are selectable by the operator, it is important to be assured that all the selected channels are contributing to the combined information display. Otherwise, it will be difficult to rely on the data being shown.
In copending application, U.S. Ser. No. 258,265, filed on Oct. 14, 1988, in the name of Jonathan Castle and entitled "Wireless Weighing System", there is described an electronic weighing system which includes a central control and a plurality of remote weighing pads. The system is provided with a bidirectional infra-red communications system which allows the central control to interrogate each weighing pad and to receive an information signal containing the measured weight of the load on the pad. Further, the weighing system includes means for displaying those weights and various combinations of them, such as cross weights, diagonal weights, percentages of total and total weight.
The system described by Castle is also extremely flexible in that all channels, or less than all channels, may be selected for measurement, display or combination. It would be extremely advantageous to provide a clear annunciation to the operator of such system which among the several communication channels (weighing pads) available for measurement are selected and which are operating correctly. The annunciation to have the greatest impact should be readily decipherable by the operator and should not be easily confused with other information sources of the system.